fix warnings about missing destructors in FeatureDetector and DescriptorExtractor classes and their derivatives

Fixed CMake cached variables

 "error: explicit template specialization cannot have a storage class"

- Save current screen (CTRL+S), with png, jpg, jpeg, bmp format support
- OpenGL rendering enable (make Qt very fast)
      -> working on opengl callback (done soon)
- Rendering optimised (with and without openGL)

Corrected Mask operator (from documentation mask must be a char matrix with non-zero values in the region of interest)

Commenting out CV_CameraCalibrationBadArgTest because a crash in its constructor prevents opencv_test to run anything

- fixed bug ticket #412

- save/load window parameters implemented !

fixed the output disparity at the extreme cases (minDisparity or minDisparity + numOfDisp - 1). Thanks to Patrick Mihelich for the report (trac #395)

- imgregion shortcut implemented (CTRL+O)